System and method for measuring/evaluating moving image quality of screen

ABSTRACT

A screen motion image quality measuring/evaluating apparatus according to the present invention comprises: a rotatable mirror  2 ; a camera  3  for capturing a screen through the mirror  2 ; and a control unit  6 . The control unit  6  is arranged to control such that when it is detected based on a change in the luminance of a screen  5  that a test pattern contained in a motion image displayed on the screen  5  has passed a predetermined position of the screen  5 , a trigger for rotation is given to the mirror  2 , and such that after the start of rotation of the mirror  2 , the mirror  2  rotates as keeping pace with the movement of the test pattern. Without electric synchronism of rotation with a motion image signal, a trigger for rotation can be given to the mirror  2 . Thus, the quality of a motion image on the screen can be measured with a simple structure.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to screen motion image qualitymeasuring/evaluating apparatus and method capable of measuring andevaluating, based on the movement of a test pattern displayed on thescreen of a display device to be evaluated, the quality of a motionimage on the screen.

2. Description of Related Art

It has been a common practice that a motion image is displayed on thescreen of a display device such as an liquid-crystal display (LCD), acathode-ray tube display (CRT), a plasma display (PDP), anelectroluminescence display (EL) or the like and the movement on thescreen is measured to evaluate the motion image quality. Examples ofthis evaluating method include a method in which a camera pursues, likean eyeball, the movement of a motion image and takes its image as astill image, and the still image thus captured is evaluated fordefinition. In particular, in a display device in which the imageholding time is long like in an LCD, the image edge is blurred. Thereduction in definition is digitalized and the value thus digitalized isused as an index. This is an example of the screen motion image qualityevaluating method.

There is conventionally known a motion image quality evaluatingapparatus which comprises a rotatable mirror and a camera for taking apicture of the screen of a display device to be evaluated through themirror, and in which the mirror rotation is controlled with the use of asynchronizing signal of a motion image video signal such that thepicture can be captured as a still image (Japanese Patent Laid-OpenPublication No. 2001-54147).

In the motion image quality evaluating apparatus mentioned above,however, it is required to prepare a trigger signal for actuating themirror rotation based on the synchronizing signal of a motion imagevideo signal. This requires developing a signal preparing circuit forpreparing such a trigger signal. This takes time and costs for suchdevelopment. Accordingly, there is desired a screen motion image qualityevaluating apparatus capable of more readily preparing a trigger for therotation of the mirror.

In view of the foregoing, it is an object of the present invention toprovide screen motion image quality measuring/evaluating apparatus andmethod by which an image having pursued the movement of a motion imagedisplayed on the screen of a display device to be evaluated can beobtained on the image sensor detection screen with a simple arrangementwithout electric synchronism with a motion image video signal.

SUMMARY OF THE INVENTION

A screen motion image quality measuring/evaluating apparatus accordingto the present invention comprises: a rotatable mirror; an image sensorfor capturing a screen through the mirror; a rotational driving unit forrotationally driving the mirror; a control unit connected to therotational driving unit; and an image processing unit, the control unitbeing arranged such that when it is detected based on a change in theluminance of a detection screen of the image sensor that a test patterndisplayed on the screen has passed a predetermined position on thescreen, a rotational driving signal is supplied to the rotationaldriving unit such that the mirror starts rotating as keeping pace withthe movement of the test pattern (Claim 1).

According to the above-mentioned arrangement, when it is detected basedon a change in the luminance of the detection screen of the image sensorthat the test pattern contained in a motion image displayed on thescreen has passed a predetermined position on the screen, the controlunit can give, based on a detection signal, a trigger for rotation tothe rotational driving unit. After the mirror has started rotating, thecontrol unit controls such that the mirror rotates as keeping pace withthe movement of the test pattern. Accordingly, without electricsynchronism with a motion image signal, a still image according to themovement of the test pattern can be obtained on the detection screen ofthe image sensor.

After the test pattern displayed on the screen has started moving, thescreen is captured more than once by the image sensor, and it can bedetected, based on the images thus captured more than once, whether ornot the test pattern has passed a predetermined position of the screen(claim 2).

The present invention may be arranged such that the test patternrepeatedly appears on the screen and moves in the same direction at thesame velocity, that the control unit is arranged to observe the image ofthe test pattern appearing on the detection screen of the image sensorduring the rotation of the mirror, and to determine the mirrorrotational velocity at which the image stands still, and that therotational driving signal supplied to the rotational driving unitcomprises information instructing that the mirror rotates at therotational velocity thus determined (Claim 3). According to theabove-mentioned arrangement, during the rotation of the mirror, the testpattern is captured and the resulting image is observed. This imagestands still when the mirror perfectly keeps pace with the movement ofthe test pattern. Accordingly, the mirror rotational velocity at whichthe image stands still can be determined as an optimum rotationalvelocity. Whether or not the image stands still may be judged, forexample, whether or not the edge in which the image is contained appearson the same position at each capturing.

The present invention may be arranged such that the test patternrepeatedly appears on the screen and moves in the same direction at thesame velocity, that the control unit is arranged to observe a testpattern blurred edge width which appears, along the scanning direction,on the detection screen of the image sensor during the rotation of themirror, and to determine the mirror rotational velocity at which theblurred edge width is minimized, and that the rotational driving signalsupplied to the rotational driving unit comprises informationinstructing that the mirror rotates at the rotational velocity thusdetermined (Claim 4). According to the above-mentioned arrangement,during the rotation of the mirror, the test pattern is captured and itsblurred edge width is observed. This blurred edge width is minimizedwhen the mirror perfectly keeps pace with the movement of the testpattern. Accordingly, the mirror rotational velocity at which theblurred edge width is minimized can be determined as an optimumrotational velocity.

Preferably, the image processing unit is arranged to evaluate the screenmotion image quality with the use of the minimized blurred edge width(Claim 5). The minimized blurred edge width serves as a parameterindicating the quality of a motion image on the screen. Accordingly, thescreen motion image quality can be evaluated with the use of the blurrededge width.

In addition to the still image judging method and the blurred edge widthobserving method, there are methods of optimizing the mirror rotationalvelocity. The control unit may be arranged to calculate the movingvelocity of the test pattern based on the movement of the test patternappearing on the detection screen of the image sensor while the mirroris fixed, and to determine the mirror rotational velocity based on thetest pattern moving velocity thus calculated (Claim 6).

A screen motion image quality measuring/evaluating apparatus accordingto the present invention comprises: a rotatable mirror; an image sensorfor capturing a screen through the mirror; a rotational driving unit forrotationally driving the mirror; a control unit connected to therotational driving unit; and an image processing unit, the test patternrepeatedly appearing on the screen and moving in the same direction atthe same velocity, and the control unit being arranged to observe theimage of the test pattern appearing on the detection screen of the imagesensor during the rotation of the mirror, to determine the mirrorrotational velocity at which the image stands still, and to rotationallydrive the mirror at the rotational velocity thus determined (Claim 8).According to the above-mentioned arrangement, the test pattern iscaptured during the rotation of the mirror and the resulting image isobserved. This image stands still when the mirror perfectly keeps pacewith the movement of the test pattern. Accordingly, the mirrorrotational velocity at which the image stands still can be determined asan optimum rotational velocity. Whether or not the image stands stillmay be judged for example whether or not the edge in which the image iscontained appears on the same position at each capturing. Thus, themirror optimum rotational velocity can be determined without knowing thestructural constants of the screen motion image qualitymeasuring/evaluating apparatus.

A screen motion image quality measuring/evaluating apparatus accordingto the present invention comprises: a rotatable mirror; an image sensorfor capturing a screen through the mirror; a rotational driving unit forrotationally driving the mirror; a control unit connected to therotational driving unit; and an image processing unit, the test patternrepeatedly appearing on the screen and moving in the same direction atthe same velocity, and the control unit being arranged to observe a testpattern blurred edge width which appears, along the scanning direction,on the detection screen of the image sensor during the rotation of themirror, to determine the mirror rotational velocity at which the blurrededge width is minimized, and to rotationally drive the mirror at therotational velocity thus determined (Claim 9).

According to the above-mentioned arrangement, the test pattern iscaptured during the rotation of the mirror and its blurred edge width isobserved. This blurred edge width is minimized when the mirror perfectlykeeps pace with the movement of the test pattern. Accordingly, themirror rotational velocity at which the blurred edge width is minimizedcan be determined as an optimum rotational velocity, and the mirror isso controlled as to rotate at the rotational velocity thus determined.Thus, the mirror optimum rotational velocity can be determined withoutknowing the structural constants of the screen motion image qualitymeasuring/evaluating apparatus. When the mirror rotates at thisrotational velocity, a still image according to the test patternmovement can be obtained on the detection screen of the image sensor.

Preferably, the image processing unit is arranged to evaluate thequality of a motion image on the screen with the use of the minimizedblurred edge width (Claim 10). The minimized blurred edge width servesas a parameter indicating the quality of a motion image on the screen.Accordingly, the screen motion image quality can be evaluated with theuse of the blurred edge width.

A screen motion image quality measuring/evaluating method according tothe present invention is arranged to measure and evaluate, based on themovement of a test pattern displayed on the screen of a display deviceto be evaluated, the quality of a motion image on the screen, and thismethod comprises the steps of: capturing an image of the test patternwhile the test pattern is moved on the screen at a predeterminedvelocity and while the visual field of an image sensor is moved on thescreen; and determining the moving velocity of the image sensor visualfield at which the test pattern image position stands still, andevaluating the quality of a motion image on the screen based on the testpattern image captured at the velocity thus predetermined (Claim 12).According to this method, while the image sensor visual field is moved,the test pattern under movement is captured and the resulting image isobserved. When the image sensor visual field perfectly keeps pace withthe movement of the test pattern, the image stands still. Accordingly,the moving velocity of the image sensor visual field at which the imagestands still can be determined as an optimum moving velocity, and thequality of a motion image on the screen can be evaluated based on thetest pattern still image captured at the velocity thus determined.Whether or not the image stands still may be judged, for example,whether or not the edge in which the image is contained, appears on thesame position at each capturing.

A screen motion image quality measuring/evaluating method according tothe present invention is arranged to measure and evaluate, based on themovement of a test pattern displayed on the screen of a display deviceto be evaluated, the quality of a motion image on the screen, and thismethod comprises the steps of: capturing an image of the test patternwhile the test pattern is moved on the screen at a predeterminedvelocity and while the visual field of an image sensor is moved on thescreen; observing a blurred edge width appearing, along the scanningdirection, on the test pattern image thus captured; and determining themoving velocity of the image sensor visual field at which the blurrededge width is minimized, and evaluating the quality of a motion image onthe screen based on the test pattern image captured at the velocity thuspredetermined (Claim 13). According to this method, while the imagesensor visual field is moved, the test pattern under movement iscaptured and its blurred edge width is observed. When the image sensorvisual field perfectly keeps pace with the movement of the test pattern,the blurred edge width is minimized. Accordingly, the moving velocity ofthe image sensor visual field at which the blurred edge width isminimized can be determined as an optimum moving velocity, and thequality of a motion image on the screen can be evaluated based on thetest pattern still image captured at the velocity thus determined.

A screen motion image quality measuring/evaluating apparatus accordingto the present invention may comprise: a rotatable mirror; an imagesensor for capturing a screen through the mirror; a rotational drivingunit for rotationally driving the mirror; a control unit connected tothe rotational driving unit; and an image processing unit, and the testpattern may repeatedly appear on the screen and may move in the samedirection at the same velocity, and the control unit may be arranged tocalculate the moving velocity of the test pattern based on the movementof the test pattern appearing on the detection screen of the imagesensor while the mirror is fixed, to determine the mirror rotationalvelocity based on the test pattern moving velocity thus calculated, andto rotationally drive the mirror at the rotational velocity thusdetermined (Claim 14). With the above-mentioned arrangement, too, whenit is supposed that the test pattern repeatedly appears on the screenand moves in the same direction at the same velocity, (i) one testpattern is captured while the mirror is fixed, (ii) the moving velocityof the test pattern is calculated based on the movement of the testpattern on the detection screen of the image sensor, (iii) the optimumrotational velocity of the mirror is determined based on the testpattern moving velocity thus calculated, and (iv) the mirror iscontrolled so as to rotate at the rotational velocity thus determined.Accordingly, a still image according to the test pattern movement can beobtained on the detection screen of the image sensor.

A screen motion image quality measuring/evaluating method according tothe present invention is arranged to measure and evaluate, based on themovement of a test pattern displayed on the screen of a display deviceto be evaluated, the quality of a motion image on the screen, and thismethod comprises the steps of: capturing an image of the test patternmore than once while the test pattern is moved on the screen at apredetermined velocity and while the visual field of an image sensor isfixed on the screen; observing the moving velocity, on the detectionscreen, of the test pattern image thus captured; and calculating anddetermining the moving velocity of the image sensor visual fieldcorresponding to the moving velocity of the test pattern image on thedetection screen, and evaluating the quality of a motion image on thescreen based on the test pattern image captured at the velocity thusdetermined (Claim 16). The quality of a motion image on the screen canbe evaluated based on the test pattern still image captured at thevelocity thus determined.

The present invention may be realized by comprising a rotatable cameraand a rotational driving unit for rotationally driving the camera,instead of: the rotatable mirror; the image sensor for capturing ascreen through the mirror; and the rotational driving unit forrotationally driving the mirror (Claims 7, 11, 15). If light in weight,the camera can be rotated according to the movement of the test patternwith a less rotational driving force.

According to the present invention discussed in the foregoing, thecontrol unit is arranged to give a trigger for rotation to therotational driving unit, and to control the mirror so as to rotate askeeping pace with the movement of the test pattern. Accordingly, withoutany electric synchronism with a motion image signal, a still imagehaving pursued the movement of the test pattern can be obtained on thedetection screen of the image sensor. Accordingly, the quality of amotion image on the screen can be measured and evaluated with a simplestructure.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram illustrating the arrangement of a screenmotion image quality measuring/evaluating apparatus according to anembodiment of the present invention;

FIG. 2 is a view illustrating the positional relationship between adetection face 31 of a CCD camera 3 and a screen 5 of a display deviceto be evaluated;

FIG. 3 is a view illustrating the movement of a test pattern P displayedon the detection face 31 of the CCD camera 3 when the test pattern P ismoving on the screen 5 at a uniform velocity;

FIG. 4 is a graph illustrating the relationship between the CCD cameraexposure amount and time;

FIG. 5 is a view illustrating how the image of the test pattern P moveson the detection face 31 of the CCD camera 3;

FIG. 6 shows luminance distributions of images detected more than onceby the CCD camera detection face 31 during the rotation of agalvanometer mirror 2, in which FIG. 6(a) shows the luminancedistribution at the time when the rotational velocity is not proper,while FIG. 6 (b) shows the luminance distribution at the time when therotational velocity is proper;

FIG. 7 is a graph illustrating the relationship between the CCD cameraexposure amount and time;

FIG. 8 shows luminance distributions of images detected by the CCDcamera detection face 31 during the rotation of the galvanometer mirror2, in which the broken line shows the luminance distribution at the timewhen the rotational velocity is not proper, while the solid line showsthe luminance distribution at the time when the rotational velocity isproper;

FIG. 9 shows how the image of the test pattern P moves on the detectionface 31 of the CCD camera 3, in which FIG. 9(a) shows the image of thetest pattern P at the initial stage immediately after the start ofmovement, while FIG. 9(b) shows the image of the test pattern P whichhas reached in the vicinity of the center of the detection face 31 ofthe CCD camera 3;

FIG. 10 shows a luminance distribution of the image of the test patternP detected, at the initial stage immediately after the start ofmovement, by the CCD camera detection face 31;

FIG. 11 shows a luminance distribution of the image of the test patternP detected, at an intermediate stage after the start of movement, by theCCD camera detection face 31;

FIG. 12 shows a luminance distribution of the image of the test patternP detected, at the initial stage immediately after the start ofmovement, by the CCD camera detection face 31; and

FIG. 13 shows a luminance distribution of the image of the test patternP detected, at an intermediate stage after the start of movement, by theCCD camera detection face 31.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The following description will discuss in detail embodiments of thepresent invention with reference to the attached drawings.

Arrangement of the Measuring Apparatus

FIG. 1 is a block diagram illustrating the arrangement of a screenmotion image quality measuring/evaluating apparatus according to thepresent invention. This apparatus comprises a galvanometer mirror 2 anda CCD camera 3 for capturing, through the galvanometer mirror 2, ascreen 5 of a display device to be evaluated.

The galvanometer mirror 2 comprises: a permanent magnet rotatablydisposed in a magnetic field generated by applying an electric currentto a coil; and a mirror mounted on a rotary shaft of the permanentmagnet such that the mirror can be smoothly and quickly rotated.

The CCD camera 3 has a visual field covering a part or whole of thescreen 5 of the display device to be evaluated. The galvanometer mirror2 is disposed between the CCD camera 3 and the screen 5. According tothe rotation of the galvanometer mirror 2, the visual field of the CCDcamera 3 can be moved on the screen 5 in a one-dimensional direction(hereinafter referred to as the scanning direction). A computer controlunit 6 is arranged to send a rotation signal to the galvanometer mirror2 through a galvanometer mirror drive controller 7. An image signalobtained by the CCD camera 3 is fetched by the computer control unit 6through an image fetching I/O board 8.

Instead of the arrangement in which the galvanometer mirror 2 and theCCD camera 3 are separately disposed, a CCD camera such as alight-weight digital camera or the like may be disposed on a rotarystand and rotationally driven by a rotational driving motor.

The computer control unit 6 is arranged to send, to an image signalgenerator 9, a display control signal for selecting the display screen5. Based on the display control signal, the image signal generator 9supplies, to the display device to be evaluated, an image signal (whichis stored in an image memory 9 a) for displaying in motion a testpattern P. Further, a liquid-crystal display 10 is connected to thecomputer control unit 6.

FIG. 2 is an optical path view illustrating the positional relationshipbetween the detection face 31 of the CCD camera 3 and the screen 5 ofthe display device to be evaluated. The light ray on the screen 5 fromthe visual field 33 of the CCD camera 3 is reflected by the galvanometermirror 2, then incident upon the lens of the CCD camera 3 and thendetected by the detection face 31 of the CCD camera 3. At the back sideof the galvanometer mirror 2, a mirror image 32 of the detection face 31of the CCD camera 3 is drawn by a broken line.

It is now supposed that the distance along the optical path between thedisplay device to be evaluated and the galvanometer mirror 2 is L, thatthe distance along the optical path between the display device to beevaluated and the lens is a, and that the distance between the lens andthe detection face 31 is b. Here, when the focal distance f of the lensis known, the relationship between a and b can be obtained with the useof the following equation:1/f=1/a+1/b

The coordinates in the scanning direction of the screen 5 of the displaydevice to be evaluated are designated by X. The detection coordinates inthe scanning direction on the detection face 31 of the CCD camera 3 aredesignated by Y. The original point X0 of X is set at the center of thescreen of the display device to be evaluated, and the original point Y0of Y is set at the point corresponding to the original point X0. When Mis the magnification of the lens of the CCD camera 3, the followingequation is established:X=−MY(M>0)

With the use of a and b mentioned above, the magnification M isexpressed as follows:M=b/a

Now, when the galvanometer mirror 2 is rotated by an angle θ, thecorresponding position on the screen 5 of the display device to beevaluated is shifted by an angle 2 θ with respect to the center of therotary shaft of the galvanometer mirror 2. The coordinates X on thescreen 5 of the display device to be evaluated which correspond to thisangle 2θ are expressed as follows:X=L tan 2θ

When this equation is modified, the following equation is obtained:θ=arctan (X/L)/2

When the equation X=L tan 2θ is differentiated with respect to time, thefollowing equation is obtained:v=2Lωcos⁻²(2θ)  (a)

wherein v is the moving velocity on the screen of the visual field 33, ωis the rotational angular velocity of the galvanometer mirror 2(ω=dθ/dt). When θ is a very small angle, cos²(2θ) can be regarded as 1.Accordingly, the above equation can be expressed as follows:ω=v/2L  (b)

Thus, it can be considered that the moving velocity v on the screen ofthe visual field 33 and the rotational angular velocity ω of thegalvanometer mirror 2 are in a proportional relationship.

Rotation Control of the Galvanometer Mirror

It is now supposed that the test pattern is an edge vertical to thescanning direction X on the screen 5. It is now supposed that the testpattern moves at uniform velocity in the +X direction on the screen 5 ofthe display device to be evaluated. It is now supposed that theluminance of a portion in the +X direction at the front with respect tothe edge is high, and that the luminance of a portion in the −Xdirection at the back with respect to the edge is low.

FIG. 3 is a view illustrating the movement of the test pattern Pdisplayed on the detection face 31 of the CCD camera 3 when the testpattern P moves at uniform velocity on the screen 5. The axis ofordinates represents time t, while the axis of abscissas represents theX coordinate. It is now supposed that the galvanometer mirror 2 is fixedat time ta through tb, and that the galvanometer mirror 2 is underrotation at time tc through tf.

While the galvanometer mirror 2 is fixed after the test pattern P hasstarted moving, a short period of time is set as the exposure time ofthe CCD camera 3 and a picture is frequently taken at short timeintervals. On the detection face 31 of the CCD camera 3, the image ofthe test pattern P (i.e., the edge) is moved, according to the movementof the test pattern P, in the −Y direction at each capturing.

For example, it is now supposed that the number of picture elements inthe transverse direction is 1024, and that the test pattern P passesthrough the 1024 picture elements in 1.4 second. For example, it is nowsupposed that the exposure time of the CCD camera 3 is set at 1/20seconds, and that a picture is frequently taken at time intervals of 0.1second.

FIG. 4 is a graph illustrating the relationship between the exposureamount of the CCD camera 3 and time when a picture is frequently takenin the above-mentioned manner.

With reference to FIG. 5, the description will discuss how to determinetimings at which a trigger for rotation is given to the galvanometermirror 2. FIG. 5 is a view illustrating how the image of the testpattern P moves on the detection face 31 of the CCD camera 3 at velocityvp. At predetermined positions of the detection face 31 of the CCDcamera 3, there are two zones A, B adjacent to each other in the −Ydirection. Setting of the zones A, B is made by the computer controlunit 6.

The computer control unit 6 detects (i) the capturing point of time (forexample, ta in FIG. 4) at which the test pattern P covers the zone Asubstantially in its entirety, but does not enter the zone B, and (ii)the capturing point of time (for example tb in FIG. 4) at which the testpattern P covers the whole zone A and subsequently enters a part of thezone B. More specifically, the computer control unit 6 detects the pointof time at which the average luminance in the zone A does not change andthe average luminance in the zone B undergoes a change in the decreasedirection. This point of time (tb) is referred to as the timing of atrigger for the rotation of the galvanometer mirror 2. When the zones A,B are set as vertically long, the number of picture elements isincreased, thus further improving the trigger timing detectionprecision.

Thus, the zones are formed on the detection face 31 of the CCD camera 3and trigger timing is detected. It is therefore possible to give atrigger for rotation to the galvanometer mirror 2 when the test patternP arrives at a predetermined position in the detection face 31.

After a trigger for rotation has been given to the galvanometer mirror2, it is required to set the rotational angular velocity of thegalvanometer mirror 2 to an optimum value. When the rotational angularvelocity of the galvanometer mirror 2 is proper, the image of the testpattern P stands still and a relatively sharp edge appears in thedetection face 31 of the CCD camera 3. If the rotational angularvelocity is not proper, the image of the test pattern P unsteadilymoves, during light exposure, on the detection face 31 of the CCD camera3, causing the edge image to get blurred. This includes not onlyblurring based on the motion image quality of the display device to beevaluated, but also blurring based on the disagreement of the rotationalangular velocity of the galvanometer mirror 2 with respect to the movingvelocity of the test pattern P.

FIG. 6 shows images of the test pattern P on the detection face 31 ofthe CCD camera 3 after a trigger for rotation has been given to thegalvanometer mirror 2. That is, FIG. 6 shows luminance distributions ofimages detected by the CCD camera detection face 31 while thegalvanometer mirror 2 is under rotation. In FIG. 6, the axis ofabscissas represents the picture elements arranged in the scanningdirection, while the axis of ordinates represents the luminance. In FIG.6, “Imax, th” is the luminance lowered by a certain rate (for example10%) from the maximum luminance, while “Imin, th” is the luminanceincreased by a certain rate (for example 10%) from the minimumluminance.

When the rotational angular velocity of the galvanometer mirror 2pursues perfectly the test pattern P, the images of the test pattern Peven taken more than once stand still and the edge appears relativelysharply on the detection face 31 of the CCD camera 3 as shown in FIG.6(b). If the rotational angular velocity of the galvanometer mirror 2does not pursue the test pattern P, each image of the test pattern Pmoves in the +Y or −Y direction on the detection face 31 of the CCDcamera 3 every time the image is taken, as shown in FIG. 6 (a).

Images are captured with the rotational angular velocity of thegalvanometer mirror 2 changed. When the edge position is moved at eachcapturing as shown in FIG. 6 (a), it can be said that the rotationalangular velocity of the galvanometer mirror 2 is not proper. Therotational angular velocity of the galvanometer mirror 2 at which theedge position is fixed as shown in FIG. 6 (b) is determined as anoptimum velocity. This rotational angular velocity of the galvanometermirror 2 is not required to be calculated with the use of the equation(a) or (b). Accordingly, the optimum rotational angular velocity of thegalvanometer mirror 2 can be determined without knowing the structure ofthe measuring apparatus (L or 0).

The following description will discuss another method of determining therotational angular velocity of the galvanometer mirror 2. According tothis method, the computer control unit 6 is arranged to control suchthat, as shown in FIG. 7, the state of light exposure of the CCD camera3 is maintained for a predetermined period of time t′ during therotation of the galvanometer mirror 2 after a trigger for rotation hasbeen given to the galvanometer mirror 2. The “predetermined period oftime” during which the state of light exposure of the CCD camera 3 ismaintained may be set to a period of time during which the motion imagequality on the screen 5 is measured and evaluated with high precision.The state of light exposure may always be maintained for a predeterminedperiod of time, or the shutter may be opened/closed more than onceduring this predetermined period of time.

FIG. 8 shows luminance distributions of images detected by the CCDcamera detection face 31 when the state of light exposure of the CCDcamera 3 is maintained for the predetermined period of time t′. In FIG.8, the axis of abscissas represents the picture elements arranged in thescanning direction, while the axis of ordinates represents theluminance. The number of picture elements between the luminance Imax, thlowered by a certain rate (for example 10%) from the maximum luminance,and the luminance Imin, th increased by a certain rate (for example 10%)from the minimum luminance is called a “blurred edge width BEW”(represented by B, B0 in FIG. 8).

When the rotational angular velocity of the galvanometer mirror 2pursues perfectly the test pattern P, the image of the test pattern Pstands still and the edge appears relatively sharply on the detectionface 31 of the CCD camera 3. If the rotational angular velocity of thegalvanometer mirror 2 does not pursue the test pattern P, the image ofthe test pattern P moves in the +Y or −Y direction on the detection face31 of the CCD camera 3, causing the edge image to get blurred.

In FIG. 8, the broken line shows the luminance distribution obtained atthe time when the rotational angular velocity ω of the galvanometermirror 2 is not proper. At this time, the blurred edge width isdesignated by B. The solid line shows the luminance distributionobtained at the time when the rotational angular velocity ω of thegalvanometer mirror 2 is proper. At this time, the blurred edge width isminimized. This minimum blurred edge width is designated by B0.

Images are captured with the rotational angular velocity ω of thegalvanometer mirror 2 changed. Then, the rotational angular velocity ofthe galvanometer mirror 2 at which such a minimum blurred edge width B0is obtained can be determined as an optimum rotational angular velocityω of the galvanometer mirror 2. In this method, too, the optimumrotational angular velocity ω of the galvanometer mirror 2 is notrequired to be calculated with the use of the equation (a) or (b).Accordingly, the optimum rotational angular velocity ω of thegalvanometer mirror 2 can be determined without knowing the structure ofthe measuring apparatus (L or θ).

The minimum blurred edge width B0 includes a blurred edge width B′ ofthe optical system such as the lens or the like. Accordingly, it isdesired that with the galvanometer mirror 2 fixed, the stationary testpattern P is captured to obtain the blurred edge width B′ of the opticalsystem such as the lens or the like, and that this blurred edge width B′is subtracted from the blurred edge width B0 to obtain a net blurrededge width B0.

When a plurality of moving velocities vp of the test pattern P are setand a minimum blurred edge width B0 is obtained for each of these movingvelocities vp, the blurred edge width B0 becomes a function of themoving velocity vp of the test pattern P. As the moving velocity vp isfaster, the blurred edge width B0 is wider. As the moving velocity vp isslower, the blurred edge width B0 is narrower. Accordingly, the blurrededge widths B0 are plotted with respect to the moving velocities, andthe inclination (time in unit) thus obtained is defined as N_BEW. It isknown that the BEW normalized by the moving velocity, i.e., N_BEW isequivalent to the response time of the display device. Accordingly, themotion image quality of the display device can be evaluated with the useof N_BEW.

The following description will discuss another method of optimizing themirror rotational velocity in addition to the above-mentioned methods.

According to this method, the computer control unit 6 is arranged tocontrol such that the galvanometer mirror 2 is fixed, that a shortlight-exposure period of time is set to the CCD camera 3 and that animage is frequently captured at short time intervals. On the detectionface 31 of the CCD camera 3, the image of the test pattern P (i.e.,edge) is moved, according to the movement of the test pattern P, in the−Y direction for each capturing.

For example, it is now supposed that the number of picture elements inthe transverse direction is 1024, and that the test pattern P passesthrough 1024 picture elements in 1.4 seconds. For example, it is nowsupposed that the light-exposure time of the CCD camera 3 is set at 1/20second, and that a picture is frequently taken at time intervals of 0.1second.

A plural number of capturings is represented by N (N=1, 2, 3, . . . ,14). FIG. 9(a) shows the image of the test pattern P captured, forexample, at N=1 (first time) when the test pattern P starts moving,while FIG. 9(b) shows the image of the test pattern P captured, forexample, at N=7 (seventh time) when the edge of the test pattern Preaches the center of the detection face 31 of the CCD camera 3.

FIG. 10 to FIG. 13 show luminance distributions of images detected bythe CCD camera detection face 31. In FIG. 10 to FIG. 13, the axis ofabscissas represents the picture elements arranged in the scanningdirection, while the axis of ordinates represents the luminance(relative value). Each graph is discontinuous because the pictureelements on the CCD camera detection face 31 are discretely arranged.

FIG. 10 shows a luminance distribution at the capturing point of timeN=1. The luminance rises up from a position of the small number ofpicture elements (about 50) at the left side of the CCD camera detectionface 31. It is now supposed that the number of picture elements havinghigh luminance is counted as M1. FIG. 11 shows a luminance distributionat the capturing point of time N=7. The luminance rises up from aposition of the intermediate number of picture elements (about 550) atthe center of the CCD camera detection face 31. It is now supposed thatthe number of picture elements having high luminance is counted as M7.

Based on FIGS. 10 and 11, when the difference (M1−M7) between thenumbers of picture elements having high luminance, is calculated, andthe value thus calculated is multiplied by the picture element pitch andthen divided by the passage period of time from N=1 to N=7, the scrollvelocity on the CCD camera detection face 31 can be calculated.

FIG. 12 shows a luminance distribution at the capturing point of timeN=1. To detect the boundary of the luminance rise, a threshold is set,and the picture element position S1 where the luminance exceeds thethreshold is referred to as the test pattern edge. FIG. 13 shows aluminance distribution at the capturing point of time N=7. To detect theboundary of the luminance rise, a threshold is set. The picture elementposition where the luminance exceeds the threshold is designated by S7.When the difference (S7−S1) between the picture element positions ismultiplied by the picture element pitch, and then divided by the passageperiod of time from N=1 to N=7, the scroll velocity of the test patternon the CCD camera detection face 31 can be calculated.

In the manner discussed in the foregoing, the scroll velocity of thetest pattern on the CCD camera detection face 31 can be calculated. Thisscroll velocity is equivalent to “v” in the equation (a) or (b)mentioned earlier. Accordingly, with the use of the equation (a) or (b),the rotational angular velocity ω of the galvanometer mirror 2corresponding to v can be obtained.

According to the embodiment of the present invention discussed in theforegoing, control is made such that there determined, based on adetection signal of the test pattern P contained in a motion imagedisplayed on the screen 5, the rotational angular velocity of thegalvanometer mirror 2 which pursues the movement of the test pattern P,and that a trigger for rotation is given to the galvanometer mirror 2such that the galvanometer mirror 2 is rotated at the angular velocitycorresponding to the moving velocity of the test pattern P. Accordingly,even without electric synchronism with a motion image signal, thereobtained, on the image sensor detection screen 5, an image whichperfectly keeps pace with the movement of a motion image. Based on theimage thus obtained, the motion image quality on the screen 5 can beevaluated.

In the foregoing, embodiments of the present invention have beendiscussed. However, the present invention should not be construed aslimited to the above-mentioned embodiments. In the present inventiondiscussed in the foregoing, the movement of the test pattern isone-dimensional, and no information is therefore contained, on the imagedisplayed on the detection face of the CCD camera 3, in a directionvertical to the direction in which the test pattern moves. Accordingly,when a direction vertical to the movement of the test pattern representsthe sum of the picture element signals on the detection face of the CCDcamera 3, the noise components of the picture element signals can bereduced to improve the detection sensitivity.

When a color CCD camera is used as the CCD camera, an image for eachcolor can be formed on the detection face, and the differences in N_BEWamong colors can be calculated to measure a color drift. Also,measurement may be made with the use of a plurality of color filterswhich can be switched to a monochrome CCD camera. In such a case,without use of a color CCD camera, there may be produced effects similarto those produced with the use of a color CCD camera.

Instead of the galvanometer mirror, a structure comprising a mirrormounted on the rotary shaft of a stepping motor or a servomotor may beadopted. Further, as mentioned earlier, the galvanometer mirror and theCCD camera may not be disposed independently from each other, but a CCDcamera itself may be rotationally driven by a rotational driving motor.Further, a variety of modifications can be made within the scope of theinvention.

1. A screen motion image quality measuring/evaluating apparatus formeasuring and evaluating, based on the movement of a test patterndisplayed on the screen of a display device to be evaluated, the qualityof a motion image on the screen, the apparatus comprising: a rotatablemirror; an image sensor for capturing the screen through the mirror; arotational driving unit for rotationally driving the mirror; a controlunit connected to the rotational driving unit; and an image processingunit, the control unit being arranged such that when it is detectedbased on a change in the luminance of a detection screen of the imagesensor that the test pattern displayed on the screen has passed apredetermined position on the screen, a rotational driving signal issupplied to the rotational driving unit such that the mirror startsrotating as keeping pace with the movement of the test pattern.
 2. Ascreen motion image quality measuring/evaluating apparatus according toclaim 1, wherein the control unit is arranged such that after the testpattern displayed on the screen has started moving, the screen iscaptured more than once by the image sensor, and that based on theimages thus captured more than once, it is detected whether or not thetest pattern has passed a predetermined position of the screen.
 3. Ascreen motion image quality measuring/evaluating apparatus according toclaim 1, wherein the test pattern repeatedly appears on the screen andmoves in the same direction at the same velocity, the control unit isarranged to observe the image of the test pattern appearing on thedetection screen of the image sensor during the rotation of the mirror,and to determine the mirror rotational velocity at which the imagestands still, and the rotational driving signal supplied to therotational driving unit comprises information instructing that themirror rotates at the rotational velocity thus determined.
 4. A screenmotion image quality measuring/evaluating apparatus according to claim1, wherein the test pattern repeatedly appears on the screen and movesin the same direction at the same velocity, the control unit is arrangedto observe a test pattern blurred edge width which appears, along thescanning direction, on the detection screen of the image sensor duringthe rotation of the mirror, and to determine the mirror rotationalvelocity at which the blurred edge width is minimized, and therotational driving signal supplied to the rotational driving unitcomprises information instructing that the mirror rotates at therotational velocity thus determined.
 5. A screen motion image qualitymeasuring/evaluating apparatus according to claim 4, wherein the imageprocessing unit is arranged to evaluate the quality of a motion image onthe screen with the use of the minimized blurred edge width.
 6. A screenmotion image quality measuring/evaluating apparatus according to claim1, wherein the test pattern repeatedly appears on the screen and movesin the same direction at the same velocity, the control unit is arrangedto calculate the moving velocity of the test pattern based on themovement of the test pattern appearing on the detection screen of theimage sensor while the mirror is fixed, and to determine the mirrorrotational velocity based on the test pattern moving velocity thuscalculated, and the rotational driving signal supplied to the rotationaldriving unit comprises information instructing that the mirror rotatesat the rotational velocity thus determined.
 7. A screen motion imagequality measuring/evaluating apparatus according to any of claims 1 to6, comprising a rotatable camera and a rotational driving unit forrotationally driving the camera, instead of: the rotatable mirror; theimage sensor for capturing the screen through the mirror; and therotational driving unit for rotationally driving the mirror.
 8. A screenmotion image quality measuring/evaluating apparatus for measuring andevaluating, based on the movement of a test pattern displayed on thescreen of a display device to be evaluated, the quality of a motionimage on the screen, the apparatus comprising: a rotatable mirror; animage sensor for capturing the screen through the mirror; a rotationaldriving unit for rotationally driving the mirror; a control unitconnected to the rotational driving unit; and an image processing unit,the test pattern repeatedly appearing on the screen and moving in thesame direction at the same velocity, and the control unit being arrangedto observe the image of the test pattern appearing on the detectionscreen of the image sensor during the rotation of the mirror, todetermine the mirror rotational velocity at which the image standsstill, and to rotationally drive the mirror at the rotational velocitythus determined.
 9. A screen motion image quality measuring/evaluatingapparatus for measuring and evaluating, based on the movement of a testpattern displayed on the screen of a display device to be evaluated, thequality of a motion image on the screen, the apparatus comprising: arotatable mirror; an image sensor for capturing the screen through themirror; a rotational driving unit for rotationally driving the mirror; acontrol unit connected to the rotational driving unit; and an imageprocessing unit, the test pattern repeatedly appearing on the screen andmoving in the same direction at the same velocity, and the control unitbeing arranged to observe a test pattern blurred edge width whichappears, along the scanning direction, on the detection screen of theimage sensor during the rotation of the mirror, to determine the mirrorrotational velocity at which the blurred edge width is minimized, and torotationally drive the mirror at the rotational velocity thusdetermined.
 10. A screen motion image quality measuring/evaluatingapparatus according to claim 9, wherein the image processing unit isarranged to evaluate the quality of a motion image on the screen withthe use of the minimized blurred edge width.
 11. A screen motion imagequality measuring/evaluating apparatus according to any of claims 8 to10, comprising a rotatable camera and a rotational driving unit forrotationally driving the camera, instead of: the rotatable mirror; theimage sensor for capturing the screen through the mirror; and therotational driving unit for rotationally driving the mirror.
 12. Ascreen motion image quality measuring/evaluating method of measuring andevaluating, based on the movement of a test pattern displayed on thescreen of a display device to be evaluated, the quality of a motionimage on the screen, the method comprising the steps of: (1) capturingan image of the test pattern while the test pattern is moved on thescreen at a predetermined velocity and while the visual field of animage sensor is moved on the screen; and (2) determining the movingvelocity of the image sensor visual field at which the test patternimage position stands still, and evaluating the quality of a motionimage on the screen based on the test pattern image captured at thevelocity thus predetermined.
 13. A screen motion image qualitymeasuring/evaluating method of measuring and evaluating, based on themovement of a test pattern displayed on the screen of a display deviceto be evaluated, the quality of a motion image on the screen, the methodcomprising the steps of: (1) capturing an image of the test patternwhile the test pattern is moved on the screen at a predeterminedvelocity and while the visual field of an image sensor is moved on thescreen; (2) observing a blurred edge width appearing, along the scanningdirection, on the test pattern image thus captured; and (3) determiningthe moving velocity of the image sensor visual field at which theblurred edge width is minimized, and evaluating the quality of a motionimage on the screen based on the image of the test pattern captured atthe velocity thus predetermined.
 14. A screen motion image qualitymeasuring/evaluating apparatus for measuring and evaluating, based onthe movement of a test pattern displayed on the screen of a displaydevice to be evaluated, the quality of a motion image on the screen, theapparatus comprising: a rotatable mirror; an image sensor for capturingthe screen through the mirror; a rotational driving unit forrotationally driving the mirror; a control unit connected to therotational driving unit; and an image processing unit, the test patternrepeatedly appearing on the screen and moving in the same direction atthe same velocity, and the control unit being arranged to calculate themoving velocity of the test pattern based on the movement of the testpattern appearing on the detection screen of the image sensor while themirror is fixed, to determine the mirror rotational velocity based onthe test pattern moving velocity thus calculated, and to rotationallydrive the mirror at the rotational velocity thus determined.
 15. Ascreen motion image quality measuring/evaluating apparatus according toclaim 14, comprising a rotatable camera and a rotational driving unitfor rotationally driving the camera, instead of: the rotatable mirror;the image sensor for capturing the screen through the mirror; and therotational driving unit for rotationally driving the mirror.
 16. Ascreen motion image quality measuring/evaluating method of measuring andevaluating, based on the movement of a test pattern displayed on thescreen of a display device to be evaluated, the quality of a motionimage on the screen, the method comprising the steps of: (1) capturingan image of the test pattern more than once while the test pattern ismoved on the screen at a predetermined velocity and while the visualfield of an image sensor is fixed on the screen; (2) observing themoving velocity, on the detection screen, of the test pattern image thuscaptured; and (3) calculating and determining the moving velocity of theimage sensor visual field corresponding to the moving velocity of thetest pattern image on the detection screen, and evaluating the qualityof a motion image on the screen based on the image of the test patterncaptured at the velocity thus determined.